1. Field of the Invention
The present invention relates to a signal processing apparatus. More specifically, the invention relates to a signal processing apparatus such as a terminal interface (DTE (data terminal equipment)--DCE (data circuit equipment) interface) used for a private high-speed modem and the like, or to a system which executes complex processing requiring a decreased number of bits in the input signals and a decreased number of bits for registers that are essentially required, such as a private high-speed data transfer apparatus using a modem, a high-speed data transfer apparatus for CATV network using a band compression system, a digital VTR and a magnetic disk apparatus.
An apparatus for supporting high-speed data requires connectors V.35/X.21 in addition to a connector V.28 recommended by ITU-T (International Telecommunication Union--Telecommunication Recommendation).
Therefore, a private high-speed modem must be equipped with the above-mentioned three kinds of connectors. That is, use of the connectors of different kinds requires three times as many instruments for maintenance as in the case in which the same kinds of connectors are usually used, and the cost for property management regarding these different kinds of connectors increases to three times as much as usual.
In these systems, it is required to collectively execute maintenance at one time in more simplified manner in a order to realize high-speed and complex signal processing at the reduced cost.
2. Description of the Related Art
In a conventional signal processing apparatus which uses several kinds of physically different connectors, signal processing functions must be separately provided by being connected to these connectors.
That is, in the conventional signal processing apparatus, the signal processing functions required by the system are separately realized by hardware, which causes problems in that the number of electric components increases and a production cost of the apparatus increases with an increase in the signal processing functions and that the quality of the signals processed by the apparatus decreases. Besides, the speed of signal processing decreases with an increase in the number of electric components.
In order to clarify the problems inherent in the conventional signal processing apparatus, described below with reference to FIG. 1 is the constitution of a terminal interface which is related to the conventional signal processing apparatus.
According to the prior art as shown in FIG. 1, the terminal interface possesses connectors 90.sub.1 to 90.sub.3 in a number equal to the number of a plurality of channels that connect to plural kinds of data terminal equipment that operates under different interface conditions and driver/receiver units 91.sub.1 to 91.sub.3 in a number equal to the number of a plurality of channels to convert levels of transmission and reception signals, the driver/receiver units 91.sub.1 to 91.sub.3 being connected to separate communication circuits.
Moreover, each communication circuit is provided with a modem for each terminal equipment.
In a conventional terminal interface related to the thus constituted signal processing apparatus, separate communication circuits and modems have been provided and connected for plural kinds of data terminal equipment that operates under different interface conditions.
When the kinds of the apparatus are to be increased, therefore, related devices such as facilities of separate circuits and switches must be newly provided resulting in an increase in the cost.